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Fuel/Temp Gauge Fix (with Pics)

I Thought I'd submit this little story to PA for future reference incase anyone else has this problem.

The Story:

I got a text a few weeks back from our illustrious mod Steve (Adrenalin) that went something like this,
"Hey Buddy, ever seen the lcd fuel and temp gauge on the lude die? Mine just did!"

So I said "no", but not wanting to risk getting hit hard by the ban stick I said “come on over and we'll check it out”.
(jokes Dude!)

So here is what we found,

Steve had the secondary cluster out of the dash when he got to my place so we removed the fuel/temp gauge from it.

We ran it up on the bench with a 12V supply. Pin 1 = 12V, Pin 10 = GND.
Sure enough it did nothing so I started looking at the Switch mode supply (it's the brown rider board pictured on the fuel/temp gauge PCB below)

(Note this is a 94 model Fuel/Temp gauge)

Honda were nice enough to label some test points on this supply so we checked them out, Vin = Battery Voltage, -8VDC and GND and two AC test points.
After checking with a multimeter we found the board had -8VDC (with respect to GND) and Vin (+12v from our power supply) but nothing between the two AC pins. I grabbed the cro to confirm but there was nothing there at all.
After tracing the AC test points through the board I found that they go straight to the display as shown below,

AC Frequency required here to power the display...

One thing I noticed was that the board smelt suspiciously like leaky caps so I removed it to have a look.

Power Supply Board Removed

Sure enough the caps had been leaking like crazy to the point where they had corroded the tracks underneath.

Corrosion on the back thanks to leaky caps

Some of the tracks were open circuit so after cleaning everything up and replacing the caps with new ones I ran jumper wires to reconnect the tracks.
I don't have a pic of that sorry.

After sorting out the power supply board I soldered it back in and hooray...It works.
The AC frequency is around 15V Peak to Peak and should look like this at the points shown in red before,

Supply for cold cathode.

Side notes,

I have a 94 model cluster (shown in the first pic) and compared to Steve's 92 cluster, the power supply board is laid out a bit differently. Also on the 94
model they used 105 degree caps instead of standard temp caps like in the 92 cluster. I guess Honda saw this as a potential point of failure and changed the design for the later models.

Anyway that's it.

So if you end up having this problem do the following (or ask someone to do it for you),

Basically remove the three electrolitic caps, clean up any corrosion, replace the caps with the same values, run wire for any tracks which are open circuit due to corrosion, re-install and you should be all good.

Hopefully this will save someone some money one day!
Any questions, feel free to PM

Scotty, I just wanted to say thank you for posting your fix. It's 2011 now, and used working gauges are much harder to find and a whole lot more expensive. EBay has them listed for roughly $180~250 USD; but with your fix, I was able to repair it in one afternoon with less than $10 USD in parts! And that includes an additional transistor and diode that needed to be replaced!

I'd like to add that my power supply was slowly deteriorating in a way where it produced more current and voltage than it should. As a result, my display ran brighter than normal, and was sending excessive current through a transistor and diode. My display gave out when both the transistor and diode blew out with a loud crackle and a pretty heavy burnt smell.

I first started my repair by replacing the blown transistor and diode; but during testing I noticed the transistor ran really hot. I figured something else must be wrong. Fortunately, I came across this thread and gave the power supply a look.

After I removed my power supply to get a good look at it's underside, lo and behold, it had the same problem with leaking electrolytic capacitors! In fact, the corrosion on my board looked exactly like your picture! Some of the corrosion was so heavy that the copper on the PCB was thin and easily broke with normal handling. I had to create wire jumpers to fix the broken copper PCB etchings.

With the three capacitors replaced and circuit board fixed, my transistor is running nice and cool now and the display is working at a normal brightness. I haven't tested it for too long (it's winter up here!), but I'm pretty confident it's all fixed.

May have to do this soon, my lcd gauges, on occasion, usually while the car has been sitting for a day or so, they start dull, then slowly warm up. Actually, I just remembered, the last time this happened was during a really rainy day too... hmmm

Also, while i have this thread necro'd.... did you find you needed quite a bit of heat on the big pins to get them desoldered? Additionally a couple of the pins had also corroded and broke during removal so I'm going to have to try and source those also. Jaycar weren't much help so it might be off to RS or Prime.

I am looking for the value of the R3 resistor on the power board. If someone could help me with that it would be greatly appreciated. I can not get a clear picture of it and the resistor was burnt so bad on my board I can not see any of the color bands. This is a 1992 Honda Prelude si that the fuel and temp gauge went out on. I am a new member and this is my first post. I am trying to repair my car as much as I do not want to at this time as my wife of 22 years of marriage just passed away four days ago. I thank you all for any help you can provide me.